phy: add Marvell HSIC 28nm PHY

Add PHY driver for the Marvell HSIC 28nm PHY. This PHY is found in PXA1928
SOC.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>